JP2023548090A - Optical device with electro-active lens - Google Patents

Abstract

The present disclosure relates to an electro-active unit for use in eyewear, the electro-active unit comprising an electro-active element, the electro-active element comprising first and second optically transparent substrates; At least one liquid crystal layer comprising a nematic liquid crystal and a Fresnel lens structure are disposed between, first and second transparent electrodes are formed on the first and second substrates, respectively, and the alignment layer is arranged on the first and second substrates. an electroactive element present on the substrate, in contact with the liquid crystal layer, and configured to align the nematic liquid crystal in a first direction, and having polarized light in a second direction that is perpendicular to the first direction. a polarizing element configured to condition the light, the liquid crystal of the liquid crystal layer being in the Morgan regime and relating to an electroactive unit.

Description

The present disclosure relates to an optical device for use in eyewear that includes a first electro-active lens for adjustable transmission of light. The present disclosure also relates to lens units including such optical devices, eyeglasses including frames provided with optical devices, and methods of operating optical devices.

An optical device comprising a liquid crystal (LC) layer and a Fresnel lens structure as part of an electro-active lens is capable of moving from a state in which the refractive index of the LC in the direction of the optical axis of the lens matches that of the lens, to a state in which the refractive index of the LC in the direction of the optical axis of the lens matches, The refractive index of the lens may be switched to a state where the refractive index of the lens does not match the refractive index of the lens. In this latter state, the lens is turned on to polarized light whose polarization angle depends on the LC alignment. A liquid crystal lens may be a lens made entirely of liquid crystals or a lens made of an isotropic material filled with liquid crystals.

Several approaches have been proposed to make such lenses suitable for non-polarized light such as natural light:
1. Two similar lenses are stacked on top of each other such that the liquid crystal alignment within each lens is perpendicular to each other (Patent Document 1).
2. A lens is used in combination with a linear polarizer in a certain orientation (Patent Document 2).

Some patent literature on liquid crystal tunable lenses describes lens stacking, but they tend to use planar alignment, where the Fresnel lens structures within the LC cavity are aligned with respect to each other. It does not take into account how it is oriented. Even so, Fresnel lens structures are generally stacked with the surfaces oriented in the same direction. For example, see Patent Document 3, Patent Document 4, Patent Document 5, Patent Document 6, Patent Document 1, or Patent Document 2.

The present disclosure relates to electro-active lenses made from isotropic polymeric materials combined with vertically aligned liquid crystals. Electro-active lenses of this type are known, for example, from US Pat. These known electro-active lenses have a number of drawbacks. For example, orientation in a plane perpendicular to the optical axis is influenced by the structure of the lenses within the optical device. This orientation is different in different parts of the optical device. Thus, in the above-described approach, the device conveys in some parts not only a magnified image but also a non-magnified image. This causes double vision.

A double image appears in the on-state of the electroactive unit when the tilt angle of the homeotropically aligned liquid crystal is small and the off-axis (with respect to unidirectionally tilted alignment) local lens surface tilt is large.

A switchable lens consisting of an isotropic polymer lens and a coated vertically aligned liquid crystal is known from US Pat. This lens is made by imprinting a polymer layer onto a single substrate. A spacer is also formed in this process, which keeps the second substrate at a constant distance from the lens. The cavity between the substrates covered with transparent electrodes is filled with liquid crystal. The alignment of liquid crystals along the substrate is determined by several factors. Orientation in the off-state is controlled by a polyimide layer that acts as an alignment layer. Generally, this layer orients the liquid crystal directors (liquid crystal director is defined as the average direction of the long molecular axes of the liquid crystal molecules) homogeneously perpendicular to the surface, also referred to as vertical alignment. When a voltage is then applied on the electrodes, the liquid crystals reorient randomly in a plane along the surface. Scraping an alignment layer on a substrate, for example a polyimide coated substrate, results in a small deflection of the director from its vertical orientation in the off state. Additional explanation of the concept of including pre-tilt by scraping alignment layers (or similar techniques such as optical alignment) in electro-active lenses is presented in US Pat. It has been incorporated.

The misalignment of the director is related to the direction of rubbing and is called pretilt. When a voltage is applied, the orientation on the substrate opposite the lens is determined solely by the rubbing direction. On substrates with lenses, the situation becomes more complicated. The orientation of the liquid crystal director is influenced by the rubbing direction and also by the geometry of the lens surface. Since the orientation of the lens surface is different at different locations, the liquid crystal director will also be non-uniform on the lens substrate. This is why in some parts the orientation of the director is different between the top and bottom substrates, resulting in twisting of the director. Note that similar alignment (i.e., application of a suitable pretilt) can be achieved by optical alignment techniques.

US Patent Application Publication No. 201715787082 U.S. Patent No. 4190330 US Patent Application Publication No. 20070216851 US Patent No. 9448456 US Patent No. 9690116 US Patent No. 10863949 US Patent No. 8,587,734 International Publication No. 2019/038439 International Publication No. 2019/101966 US Patent No. 7,724,347

V. G. Chigrinov et al. “Photoalignment of liquid crystal materials: Physics and applications” Gooch, C. H. and H. A. Tarry. “The optical properties of twisted nematic liquid crystal structures with twisted angles less than or equal to 90 degrees s” Applied Physics Vol. 8 (1975): pp. 1575-1584.

It is an object of the present disclosure to provide an optical device that includes at least one adjustable electro-active lens that provides improved optical quality and/or reduced risk of double imaging.

A further objective is to improve the optical quality and reduce the occurrence of optical artifacts such as double images when the light collected or dispersed by the electro-active lens is unpolarized.

According to a first aspect, an optical device for use in eyewear is provided, the optical device comprising a first electro-active lens for tunable focusing or dispersion of light, the electro-active lens comprising: - first and second optically transparent substrates, the first and second optically transparent substrates extending generally parallel to each other and defining axial (z) and transverse directions (x,y); , a substrate;
- a diffractive lens structure, such as a Fresnel lens structure, arranged between the first optically transparent substrate and the second optically transparent substrate on the side of the second optically transparent substrate;
- a first optically transparent electrode formed on a first optically transparent substrate and a second optically transparent electrode formed on a second optically transparent substrate or on a diffractive lens structure;
- a sealed cavity (108) between the first optically transparent substrate and the second optically transparent substrate, in which the diffractive structure and the nematic liquid crystal (LC) material are arranged; at least one LC layer is disposed, the liquid crystals in the nematic liquid crystal (LC) material being generally axially aligned in an off state;
The first optically transparent electrode has a contact surface in contact with the LC layer to linearly align the liquid crystals in the nematic liquid crystal material in the on state in the first horizontal direction by introducing a pretilt in the off state. a sealed cavity (108) comprising an alignment layer configured to;
a polarizing element configured to condition light having a polarization in a second horizontal direction that is perpendicular to the first horizontal direction;
The LC layer of nematic liquid crystal material has a thickness ( D) has
The thickness (D) is selected to satisfy the condition 1<(πD(n _e −n _o )/(φλ)<200, where n _o is the ordinary refractive index of the LC layer and n _e is the LC layer is the extraordinary refractive index of the layer, φ is the twist angle of the liquid crystal director of the LC layer, and λ is the wavelength of the light, where the wavelength λ is in the range from 350 nm to 750 nm.

The twist angle may be in the range of 0 to 180 degrees.

The pre-tilt caused by the alignment layer, and if present, further alignment layers described below, results in relatively small deviations from perfect axial alignment. In embodiments of the present disclosure, the pretilt (defining a small deviation from perfect axial (vertical) alignment) typically varies between 1 and 6 degrees with respect to the axial (z-) direction. Reference is also made to US Patent Application Publication No. 2003/0000000, filed by the same inventors, which provides further explanation of how including a small pretilt may aid in proper alignment of the LC material in the off and on states.

When this condition is met, the liquid crystal of the liquid crystal layer is well within the Mauguin regime so that waveguiding within the liquid crystal layer takes place. This allows maintaining the linear polarization of the light traveling within the optical device. Furthermore, a specific linear alignment direction can be applied to the first optically transparent electrode by using an alignment layer of the first optically transparent electrode, thus making it suitable for uniform optical devices on the surface optical device. A good response can be achieved. In addition, by maintaining linear polarization, it is possible to filter out unwanted artifacts such as double images. Filtering may, in some embodiments, be accomplished by including a linear polarizer within the optical device, while in other embodiments, the first electro-active element, as described below. This is achieved by providing a second electro-active lens stacked on top of the lens. For example, in embodiments of the present disclosure, the polarizing element described above allows light having a first linear polarization to pass through and substantially transmits light having a second linear polarization perpendicular to the first linear polarization. A polarizer (preferably a linear polarizer) configured to block the polarizer. Alternatively, or in addition, in other embodiments of the present disclosure, the polarizing element described above comprises a second electro-active lens, preferably similar to the first electro-active lens, stacked on the first electro-active lens. including an electro-active lens.

Optical devices as defined herein include first and second substrates that are substantially planar and arranged to extend generally parallel to each other; alignment layer. In these embodiments, axial alignment corresponds to vertical alignment when the flat substrate and/or the flat alignment layer are arranged to extend horizontally. In other embodiments, the first and second substrates and/or the first or second alignment layer may be curved elements that still extend generally parallel to each other. It is arranged so that it exists. In these embodiments, the axial alignment of the nematic liquid crystal (LC) material defines an alignment in a direction that is locally perpendicular to the surface of the substrate/alignment layer facing the sealed cavity. In other words, at every location on the surface, an axial direction can be defined that is a direction perpendicular to the local orientation of the surface of the substrate/alignment layer. This direction is generally different for different placements on the surface. Therefore, in embodiments having curved substrates and alignment layers, it is preferred to refer to "axial alignment" rather than "vertical alignment."

Although an alignment layer is generally required on the diffractive lens structure to axially (vertically) align the liquid crystal in the off-state, it is not strictly necessary to introduce a directional pretilt. In the on state, a non-uniform director profile exists in the diffractive lens structure, resulting in different twist angles that are highly dependent on the local diffractive lens structure. However, introducing a pretilt in the same transverse (horizontal) direction as the linear alignment direction of the alignment layer on the first optically transparent electrode generally reduces the value of the twist angle, thereby increasing the Morgan condition value. do. This results in better optical performance.

Throughout this disclosure, when referring to liquid crystals in nematic liquid crystal (LC) materials, generally axially aligned means that a substantial portion of the liquid crystals are uniaxially aligned.

According to embodiments of the present disclosure, the diffractive lens structure disposed between the first optically transparent substrate and the second optically transparent substrate on the side of the second optically transparent substrate is arranged on the side of the second optically transparent substrate. Disposed in an optically transparent layer. A second optically transparent electrode may be formed on the diffractive lens structure. According to embodiments of the present disclosure, the diffractive lens structure disposed between the first optically transparent substrate and the second optically transparent substrate on the side of the second optically transparent substrate is arranged on the side of the second optically transparent substrate. An optically transparent electrode is disposed on the second optically transparent substrate, and a second optically transparent electrode is disposed on the second optically transparent substrate.

According to embodiments of the present disclosure, the polarizing element includes a second electro-active lens stacked on the first electro-active lens. The first optically transparent layer of the first electro-active lens has a contact surface in contact with the LC layer so as to linearly align the liquid crystals in the nematic liquid crystal material in the first horizontal direction in the on state. the first optically transparent layer of the second electro-active lens has a contact surface in contact with the LC layer and in the on-state aligns the liquid crystal in the nematic liquid crystal material with the second electro-active lens. An alignment layer configured for linear alignment in a horizontal direction, the first direction being perpendicular to the second horizontal direction. In this manner, the optical device can transmit (i.e., disperse or focus) unpolarized light into the electro-active lens with improved precision, thereby eliminating the possibility of double imaging. Avoid or at least reduce.

Preferably, the refractive power of the first electro-active lens corresponds to the refractive power of the second electro-active lens, such that in the on-state of the optical device, the refractive power of the first electro-active lens is The lensing provided corresponds to a lensing for a second linear polarization direction (the second direction being orthogonal to the first direction).

The first and second electro-active lenses may be identical, which may be advantageous from a manufacturing cost point of view. However, the first and second electro-active lenses may be different as well. For example, in embodiments where the diffractive lens elements of both electro-active lenses are Fresnel lens structures, the blaze axial height and/or blaze transverse position ( The blaze transversal position) may be at least partially different from the blaze axial height and/or blaze transversal position of the Fresnel lens structure of the second electro-active lens. This may, for example, help reduce parallax and moiré effects when viewed from an oblique direction.

Additionally or alternatively, the nematic liquid crystal material of the first electro-active lens may be different from the nematic liquid crystal material of the second electro-active lens. Using different nematic liquid crystal materials can help reduce parallax and moiré effects when viewed from an oblique direction. Furthermore, the choice of nematic liquid crystal material may influence the required position of the blazes of the diffractive structure and/or reduce the occurrence of chromatic aberrations.

In some embodiments where the first and second electro-active lenses are stacked, the first optically transparent substrate of the first electro-active lens and the first optically transparent substrate of the second electro-active lens are: combined into a single common optically transparent substrate. The stack of electro-active lenses may then have only three substrates.

Instead of stacking two electro-active lenses on top of each other, a single electro-active lens can be provided with at least one linear polarizer. The linear polarizer is configured to allow light having a first linear polarization to pass therethrough and to substantially block light having a second linear polarization perpendicular to the first linear polarization. Further, the polarizer is preferably arranged on the side of the first optically transparent layer such that the first linearly polarized light is substantially parallel to the alignment of the liquid crystals in the liquid crystal layer at a location proximate to the first electrode. are aligned. In other words, the polarizer axis may be aligned with the direction of the liquid crystal director in the nematic liquid crystal (LC) material of the first electro-active lens in the on state. In this way, when unpolarized light is incident (when the optical device is in the on state), an enlarged image originating from the first polarized light along the first linear alignment direction and a second polarized light perpendicular to the first direction are generated. A non-magnified image is generated. The unmagnified image can then be easily removed by a suitable polarizer.

In a preferred embodiment, the linear polarizer comprises one or more polarizing layers attached to the first substrate and/or the first optically transparent electrode, more preferably the linear polarizer comprises an alignment layer. A polarizing layer is attached and aligned in the alignment direction of the alignment layer. Note that the alignment direction may be achieved in different manners and may correspond to the rubbing direction when the alignment layer is subjected to a rubbing action or to the photoalignment direction when the alignment layer is subjected to a photoalignment treatment. .

In a further embodiment, the optical device comprises at least one polarizing layer formed on the surface of the diffractive lens structure facing the LC layer, the polarization director of the at least one further polarizing layer being a local liquid crystal director at the lens surface. is adjusted within different regions of the diffractive lens structure to match.

The optical device is of a type in which at least one electro-active lens is configured to adjust the focusing or dispersion of light by changing the alignment of liquid crystals in the LC layer upon application of a voltage to the optically transparent electrode. It may be of. As will be understood by those skilled in the art, voltages can be applied in different ways. One example of attaching one or more electro-active lens electrodes to a power source, such as a battery located in different parts of an eyeglass frame, is described in US Pat. Furthermore, the optically transparent electrodes of the electro-active lens can be electrically connected for simultaneous switching of the first and second electro-active lenses. Adjustment of the focusing or dispersion of light can cause variations in the refractive power of the electro-active lens by changing the refractive index of the LC layer in the transverse direction upon application of a voltage across the optically transparent electrodes, since this This is because it reorients the director in the transverse direction.

The optical device is configured to change the at least one electro-active lens from an off state in which the at least one electro-active lens exhibits substantially no lens action to a state in which the at least one electro-active lens exhibits lens action upon application of a voltage to the optically transparent electrode of the at least one electro-active lens. The at least one electro-active lens may be configured to switch to an on state as shown. Depending on the type of diffractive lens element, lensing may involve magnification of the incident image.

In the off state, the liquid crystals in the nematic liquid crystal material are oriented such that the refractive index of the LC layer in the transverse direction substantially matches the refractive index of the diffractive structure, and/or in the on state, the orientation of the liquid crystals is tilted and aligned. is parallel to the alignment direction of the alignment layer.

The optical device may comprise a plurality of spacers arranged in the liquid crystal layer and extending in a direction perpendicular to the plane in which the second electrode extends, the spacers preferably being arranged above the diffractive lens structure. is formed. The spacer ensures that the required minimum and maximum thickness of the LC layer can be achieved accurately. In a specific embodiment, the spacer provides an additional height of between 1 and 20 μm, preferably between 2 and 12 μm, when measured from the part of the diffractive lens structure closest to the second substrate. It is configured as follows.

The liquid crystal material of the LC layer is preferably selected to have a birefringence Δn in the range 0.15 to 0.40.

According to another aspect, a lens unit for use in eyewear is provided, the lens unit comprising a first lens component, a second lens component, and an optical device as defined herein. , the electro-active lens is disposed between the first lens component and the second lens component, preferably sandwiched.

According to yet another aspect, eyeglasses are provided, the eyeglasses comprising a frame on which are mounted first and second lens units or first and second optical devices as defined herein.

According to yet another aspect, a method of operating an optical device comprising first and second electro-active lenses as defined herein is provided, the first electro-active lens and the first electro-active lens An alternating current voltage is applied to the first and second electrodes of the second electro-active lens stacked on top to align the liquid crystal in a direction substantially perpendicular to the first and second substrates. The present disclosure also relates to the use of optical devices, lens units, and/or eyeglasses as defined herein.

Overview Although liquid crystal is a uniaxial material, it has the property of birefringence. This is the specific phase delay
_{means that} two light rays always emerge from the liquid crystal layer with , n _e is the extraordinary refractive index, and n _o is the ordinary refractive index. The angle φ below indicates the twist angle of the liquid crystal director and varies linearly with the distance d in the z direction (ie the thickness of the LC layer). Morgan condition is
It is satisfied when . Waveguiding of the incident polarized light takes place when the Morgan condition is met. Both the extraordinary wave and the standing wave then follow the rotation of the optical axis, and the liquid crystal plays the role of polarization rotator.

In liquid crystal lenses, the refractive index of the lens material can be matched to the refractive index of the liquid crystal, ie, one of n _e or _no . This means that there is no lensing effect on linearly polarized light in the direction of matched refractive index. For polarization perpendicular to this, all light is refracted by the lens. When unpolarized light that can be resolved into two orthogonal polarization directions is transmitted, half of the light is lensed and half is not. Therefore, a double image is transmitted. In order to lens all the light, one solution is to add a second liquid crystal lens whose liquid crystal is perpendicular to the first liquid crystal lens. This is also proposed in Patent Document 10 and Patent Document 1. However, in both patents, the arrangement of the liquid crystals differs from the present disclosure in the way the two liquid crystal layers are stacked.

In the case of the present disclosure, the liquid crystal director has a non-uniform alignment on a substrate with a Fresnel lens structure, but a uniform alignment on a counter substrate (without a Fresnel lens structure). When stacking two lenses, if a substrate with a Fresnel lens structure hits the other lens, it is impossible to make the liquid crystal director perpendicular to the substrate touching the second lens in all parts of the lens. be. This is only possible if the two lenses are stacked together with opposing substrates facing each other.

Another solution to making an electro-active lens work for unpolarized light is to add a polarizer to the lens. In this case, the polarizer axis should coincide with the liquid crystal director. Since the liquid crystal director is uniform only on the opposite substrate of the lens, a (linear) polarizer should be attached to this substrate and aligned in the liquid crystal (=rubbing or light alignment) direction.

In a further solution, a polarizer is also added to the electro-active lens. However, in this case this is a special type of polarizer in which the polarizer director is adjusted within different regions of the lens to match the local liquid crystal director on the lens surface. This polarizer is attached to the lens substrate. Polarizers of this type can be made by optical alignment (see, for example, J.D.

As mentioned above, the liquid crystal twist should be widely extended in the waveguiding regime in order to have a pure splitting into one polarization for the magnified image and one polarization for the non-magnified image. This means that the Morgan condition should be satisfied, and we rewrite it for clarity as 0.5pΔn>>λ, where λ is the wavelength of the light and p is the helical pitch ( 2πd/φ), and Δn is the birefringence. Pitch is the length by which the director of the liquid crystal is twisted through 360 degrees.

For example, in some conditions λ is the wavelength of light, typically 0.5 microns. Δn is the difference in refractive index along the steady and extraordinary axes, typically 0.2, and p is the helical pitch. This means that to satisfy the Morgan condition, the helical pitch p should be significantly larger than 0.5/(0.5 x 0.2) = 5 microns, considering the alignment geometry. .

The amount of twist in an electro-active lens is such that the lens structure allows the liquid crystal to control the direction of the director between the two surfaces of the liquid crystal contact, in the case of the present application between the lens surface and the facing substrate (counter substrate). Depends on how much you change it.

Numerical calculations by finite element method were applied by the inventors to determine the torsional behavior of the liquid crystal in the electro-active lens, which was found to be dependent on the pretilt angle of the liquid crystal on the lens surface. This pretilt angle can be influenced by the alignment material, rubbing or illumination conditions, and even the surface angle of the polymer (Fresnel) lens with respect to the substrate on which it rests. Generally, the lower the pretilt, the greater the twist. For example, an 87 degree pretilt on a surface with a 3 degree angle oriented perpendicular to the alignment direction results in a total twist of 45 degrees.

Considering the cross-section of the electro-active lens perpendicular to the aligned surfaces, the torsion value changes with changing azimuthal angle. When the side of the cross section coincides with the rubbing direction, the twist between the lens and the counter substrate should be 0 degrees. However, as the azimuth changes, the value of the torsion angle increases and can theoretically reach a value of 180 degrees. In this case, the directors on the Fresnel lens surface and on the counter substrate are oriented parallel to each other, and instead of bending deformation, the directors will choose torsion. This selection occurs as the system attempts to reach equilibrium, and the overall minimum energy state corresponds to a 180 degree twist. The higher the twist value, the more the distance between the two substrates must be greater than 2.5 microns. To this end, a spacer at least 4 microns higher than the top of the blaze is applied to a 1.5 diopter lens (diameter 21 mm, Δn=0.2).

Depending on the lens power and diameter, the height of the spacer above the lens should be optimized to fill the Morgan regime across the entire lens surface.

If the conditions are met for the waveguiding/Morgan regime, the linear polarization of the light is consistent with the twisting of the liquid crystal molecules. It is this effect that the inventors have found can be used to improve the quality of electro-active lenses.

This maintains linear polarization through the lens cell, and when a linear alignment direction is applied to the opposing substrate, the optical response to this surface is uniform. More specifically, there is an enlarged image along the linear alignment direction and a non-enlarged image perpendicular thereto. Therefore, if a linear polarizer is placed on its side, the unmagnified image can be removed without any problem. Additionally, polarization independent switchability can then be achieved by stacking a similar electro-active lens on top of the first electro-active lens, provided that both counter substrates are oriented towards each other and placed at a 90 degree angle. It is also possible to make lenses.

FIG. 2 illustrates an embodiment of an optical device comprising an electro-active lens. FIG. 3 is a diagram illustrating twisting of liquid crystals within an electro-active lens. FIG. 3 is a diagram illustrating alignment of liquid crystals within an electro-active lens. FIG. 3 is a diagram illustrating the liquid crystal alignment of two liquid crystal layers of each electro-active lens. FIG. 3 is a diagram illustrating an example of polarization-dependent magnification by an electro-active lens. 1 illustrates an electro-active lens provided with a polarizer layer according to an embodiment of the present disclosure; FIG. FIG. 3 illustrates an electro-active lens provided with a polarizer layer according to another embodiment of the present disclosure. FIG. 6 illustrates an embodiment of a lens unit comprising a first lens component, a second lens component, and the optical device of FIG. 5 sandwiched between the two lens components. 2 illustrates an embodiment of an optical device comprising two stacked electro-active lenses, corresponding to the embodiment of FIG. 1; FIG. FIG. 3 illustrates an electro-active unit comprising a stack of two electro-active lenses according to the present disclosure. FIG. 3 illustrates exemplary test results for electro-active lenses according to embodiments of the present disclosure. FIG. 3 illustrates exemplary test results for electro-active lenses according to embodiments of the present disclosure. FIG. 3 illustrates exemplary test results for electro-active lenses according to embodiments of the present disclosure.

For purposes of explanation, the following description sets forth numerous specific details to provide a thorough understanding of the present disclosure. However, it may be apparent that the present disclosure may be practiced without these specific details. In other instances, well-known structures and devices have not been described in detail to avoid unnecessarily obscuring the present disclosure.

As will be apparent to those skilled in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein may be modified among several other embodiments without departing from the scope of this disclosure. has discrete components and features that can be easily separated from or combined with the features of any of the embodiments. Any described method may be performed in the described order of events or in any other order that is logically possible.

As used in this specification and the appended claims, the singular forms "a," "an," and "the" do not clearly dictate otherwise from the context. Note that this includes multiple referents. Furthermore, it is noted that the claims may be written to exclude any additional elements. As such, this text does not include the use of exclusive terms such as "solely," "only," and similar words in connection with the description of claim elements, or as a precedent to the use of "negative" limitations. meant to work.

FIG. 1 shows an electro-active lens 101. FIG. Electro-active lens 101 may be part of a lens. The electro-active lens 101 includes a first substrate 104 on which a first electrode 106 is formed, a second substrate 105 on which a second electrode 107 is formed, and the first substrate 104 and the second substrate 106. Between, certain embodiments include a volume or cavity 108 enclosed between electrodes 106 and 107 and sealed by two boundaries 103 located at opposite ends of electro-active lens 101. First substrate 104, second substrate 105, first electrode 106, and second electrode 107 may be made from optically transparent materials. For example, electrodes 106, 107 may include a tin-doped indium oxide (ITO) layer and/or an indium zinc oxide (IZO) layer. The first and second electrodes 106, 107 may be connected to a power source (not shown). The power source may be configured to apply a voltage difference between the first electrode and the second electrode when the optical device is switched to the on state, while in the off state, the voltage difference between the first and second electrodes is There is substantially no voltage difference between the electrode and the second electrode.

A sealed volume or cavity 108 between optically transparent electrodes 106, 107 includes a diffractive lens structure 102 and at least one nematic liquid crystal (LC) layer 113 formed from nematic liquid crystal. Cavity 108 of electro-active lens 101 may include a diffractive lens structure in the form of a Fresnel lens structure, although other types of diffractive structures may also be employed. The diffractive structure 102 extends over only a portion of the width of the cavity 108 in the illustrated embodiment such that there are respective intermediate spaces 108a, 108b at each end of the diffractive structure. However, in other embodiments, the diffractive structure is such that it contacts two boundaries 103, which boundaries 103 may be formed by a plug placed between the first substrate 104 and the second substrate 105. extend. Additionally, although the Fresnel lens structure 102 is positioned at the center of the cavity 108, in other embodiments the Fresnel lens structure may be located closer to any of the boundaries 103 of the electro-active lens 101. The Fresnel lens structure 103 is also made from a transparent material, for example from an isotropic polymeric material.

In addition, one or more spacers 109 may also be placed inside the volume 108. Spacer 109 may be placed between Fresnel lens structure 102 and counter electrodes 106, 107. For example, as illustrated in FIG. 1, Fresnel lens structure 102 may be disposed on second electrode 107. One or more spacers 109 are then placed between Fresnel lens structure 102 and first electrode 106 and extend through volume 108 . One or more spacers (not shown) are also disposed between the electrodes 106, 107, which extend from the first electrode 106 through the volume 108 to the second electrode 107.

Furthermore, over (or as part of) the first electrode 106, an alignment layer 111 is disposed to align the LC material 113 inside the cavity 108. Optionally, a second alignment layer 112 is disposed over the diffractive structure 102, ie, on the surface of the diffractive structure 102 facing the LC material within the cavity 108. In embodiments (not shown in FIG. 1) in which the second electrode layer is present on the diffractive structure instead of being disposed between the second substrate 105 and the diffractive structure 102, the second electrode layer The alignment layer 102 may be part of the second electrode 102 .

The electrodes 106, 107 are arranged to change the alignment of the liquid crystals in the liquid crystal (LC) layer, thereby changing the refractive index of the liquid crystal (LC) layer in the transverse direction of the electro-active lens 101 (the x direction in FIG. 1). configured. More specifically, this is the transverse (horizontal) refractive index, which must either match or not match the refractive index of the diffractive structure. Thereby, variations in the refractive power of the electro-active lens 101 may be obtained. The alignment of the liquid crystals can be changed by activation of the electro-active lens 101. Electro-active lens 101 is configured to be activated using a voltage applied to optically transparent electrodes 106, 107, as described below.

When no voltage is applied to the electrodes 106, 107, the alignment of liquid crystal molecules within a nematic liquid crystal (LC) is determined by the alignment layer. More specifically, the liquid crystal molecules in a nematic liquid crystal (LC) layer exhibit both in-plane and out-of-plane alignment, and the in-plane alignment direction of the liquid crystals typically coincides with the rubbing or illumination direction. . The average upward tilt angle of the liquid crystal from the aligned surface plane is then referred to as the (unidirectional) pretilt angle. When a voltage is applied to the electrodes 106, 107, then the electric field generated between the electrodes 106 and 107 causes different alignment directions of the liquid crystal.

For example, in a first state, also referred to herein as the off-state, with no voltage applied to the optically transparent electrodes 106, 107, the liquid crystal is The refractive index of the layer may be oriented to substantially match the refractive index of the diffractive lens structure 102. As a result, the diffractive lens structure 102 and the LC layer effectively form a combined optical layer having the same refractive index in the transverse direction (x direction) (i.e., substantially no optical interface exists within the volume 108). to form. In other words, the combined optical layers have a substantially constant refractive index within volume 108 regardless of width position (ie, position along the x direction as shown in FIG. 1). Furthermore, the combined optical layer also has two parallel surfaces. As a result, light rays incident on electro-active lens 101 when in the first state are not collimated or dispersed.

In the second state, also referred to herein as the on-state, in which a voltage is applied to the first electrode 106 and the second electrode 107, the orientation of the liquid crystal molecules typically follows the alignment of the alignment layer. direction and thus an additional optical interface is formed between the liquid crystal in the LC layer and the diffractive lens structure 102. This additional optical interface results in a different refractive index of the combined layers. Accordingly, light rays incident on the electro-active lens 101 are refracted by the optical interface between the diffractive lens structure 102 and the LC layer, thereby collimating or dispersing the light rays incident on the diffractive lens structure 102.

In summary, a first state may be a state in which no voltage is applied to the electrodes 106, 107, and a second state is a state in which a suitable voltage is applied to the electrodes 106, 107 and a transverse direction of the electro-active element 101. The refractive index of the combined optical layers matches and differs from the refractive index of the diffractive lens structure 102 (eg, a Fresnel lens structure), respectively. Similarly, in the following description, the switched-on state refers to a state in which additional refractive power is provided to the electro-active lens 101 by forming a refractive optical interface between the diffractive lens structure 102 and the liquid crystal in the volume 108. The switched-off state refers to a state in which the refractive index of the liquid crystal in the transverse direction of the electro-active lens 101 matches the refractive index of the diffractive lens structure 102 as a result of no additional optical power being provided to the electro-active lens 101. Point. Preferably, the refractive index of the LC layer (switched off state) and the Fresnel lens structure 102 also matches the refractive index of the first substrate 104 and/or the second substrate 105.

Fresnel lens structure 102 may be a positive Fresnel lens structure or a negative Fresnel lens structure. Preferably, Fresnel lens structure 102 is a negative Fresnel lens structure (as illustrated in FIG. 1). The type of Fresnel lens structure 102 used may vary depending on the application of the electro-active lens 101; for example, Fresnel lens structures 102 of different sizes, strengths, and shapes may be used. The Fresnel lens structure 102 may be placed on an electrode 107 that is connected to the second substrate, or in embodiments where the electrode is placed on the Fresnel structure 102, the Fresnel structure may be connected to the second substrate. . In embodiments where Fresnel lens structure 102 is disposed on electrode 107, Fresnel lens structure 102 may be formed on electrode 107 by any technique, such as nanoimprint lithography. Fresnel lens structure 102 may be formed by a plurality of concentric ring-like shapes called blazes 110. The blaze 110 has a side extending in the axial direction (i.e. z-direction) of the electro-active lens 101, a side facing the electrode where the Fresnel lens structure 102 is formed (i.e. the xy plane), and an oblique side (even if it is bent). It is formed by a ring-like shape with a cross-section similar to a triangular-like shape with a good angle), which provides a refractive optical interface between the Fresnel lens structure 102 and the liquid crystal in the switched-on state. The shape of the blaze 110 may be optimized for the particular application of the electro-active lens 101, and the examples or illustrative diagrams described above are non-limiting.

First substrate 104 and second substrate 105 may be joined by applying an adhesive between the two substrates, thereby forming at least a portion of boundary 103. The adhesive that bonds the first substrate 104 and the second substrate 105 may be, for example, NOA71 or NOA160. The boundary 103 or a portion of the boundary may further be formed during the formation of the Fresnel lens structure 102, for example in a nanoimprinting step in which the Fresnel lens structure 102 is formed.

The same explanation given above in view of FIG. 1 may also apply to the embodiments shown in FIGS. 5 to 7, where like reference numerals may refer to similar elements.

A nematic liquid crystal in an electro-active lens such as that in FIG. 1 can cause double refraction due to the birefringent properties of the liquid crystal. As illustrated in FIG. 4, in the on state of the electro-active lens, the electro-active lens provides lens power. However, due to the birefringent properties of liquid crystals, different polarizations are refracted differently. For example, dot 402 and dot 403 ideally coincide and form a single dot. However, due to the different refraction of the different polarizations, these dots appear separated in the magnified image 401. In the following discussion, this problem will be stated more clearly, considering FIGS. 2-4, and then how this problem is solved, considering FIGS. 5, 6, and/or 7. will be revealed. 8A-8C are exemplary measurements illustrating the success of the proposed solution.

FIG. 2 illustrates a liquid crystal layer including a liquid crystal 205 disposed between two surfaces 200, 210. Although it is a uniaxial material, liquid crystal has the property of birefringence. This is the phase delay
means that two rays with always appear in the layer, d is the layer thickness, λ is the wavelength, _ne is the extraordinary refractive index, and _no is the ordinary is the refractive index, and (n _e −n _o )=Δn is the birefringence. The angle φ in equation (1) and FIG. 2 indicates the twist angle of the liquid crystal director and varies linearly in the z-direction. When the Morgan condition is satisfied, i.e.
Waveguiding of the incident polarization occurs when . Both the extraordinary polarization and the regular polarization of the incident light then follow the rotation of the optical axis, and the liquid crystal 205 acts as a polarization rotator.

In a liquid crystal layer in an electro-active lens as described with reference to FIG. 1, the refractive lens material 102 is matched to that of the liquid crystal's refractive index, ie ( _ne or _no ). This means that there is no lensing effect on linearly polarized light in the direction of matched refractive index. For polarized light with a polarization perpendicular to this, all light will be refracted by the lens. When unpolarized light is transmitted, which can be described as a superposition of light of two orthogonal polarization directions, half of the light undergoes lensing and the other half does not undergo lensing. Therefore, a double image is transmitted.

In other words, the birefringent liquid crystal 205 disposed between surfaces 201 and 210 tends to twist about the angle φ over the distance d. As explained above, the liquid crystal 205 guides the incident polarized light when the Morgan condition is met. As such, for example, if light is incident on transparent surface 200 in the z-direction, the polarization of said light in the x-direction is different from another polarization of light with a polarization direction (at surface 200) in the y-direction. Another result is the refractive index of the liquid crystal layer.

Twisting of liquid crystal 205 is not only influenced by the thickness of the layer between surfaces 200 and 210, but can also be influenced by known methods such as alignment layer rubbing or photoalignment. Furthermore, the orientation of the second surface 210 with respect to the first surface 200 also affects the twist of the liquid crystal 205. For example, if the second surface is rotated in the yz plane, liquid crystal 205 will rotate in a different manner than currently illustrated in FIG. This may occur, for example, at the location of the blaze 110.

This may be illustrated in FIG. 3A, which illustrates a lens profile 300. Such a lens profile may be a lens that includes an electro-active lens, such as electro-active lens 101 in FIG. In the lens of FIG. 3, both the Fresnel structures 102 provided on the first electrode 106 and the second electrode 107 are provided with alignment layers, and these alignment layers are aligned in direction 306. This will likely cause alignment of the liquid crystal in both the first electrode 106 and also the Fresnel structure 102 in the direction 306. However, Fresnel structure 102 does not provide a surface parallel to the surface of first electrode 106, and as such, the surface of Fresnel structure 102 is generally indicated by arrows 301, 302, 303, 304 and 305. As illustrated, it affects the alignment of the liquid crystal thereon. Even if the alignment in the middle of the lens profile 300 (exemplified by arrow 301) is parallel to the alignment direction 306, a first lower left orientation 302, a first lower right orientation 303, a first upper left orientation 304, and The liquid crystal alignment in the first upper right orientation 305 has a substantial component that is not parallel to the rubbing direction (306). As such, applying a linear polarizer is not sufficient to obtain a single image since the output light contains multiple polarizations that cross the different refractive properties of the birefringent liquid crystal.

The above problem may be solved by placing a further electro-active lens, such as element 101 of FIG. 1, on top of the electro-active lens of profile 300 to obtain a stack of two elements with profile 310 as in FIG. 3B. It is possible to assume that. The above description also applies to additional electro-active lenses, however, any additional electro-active lenses would be aligned in a direction 316 perpendicular to alignment direction 306. In fact, the first central orientation 301 is orthogonal to the second central orientation 311 and as such a polarization independent refraction is obtained near the center of the lens profile 310. However, away from the center, for example, where the first lower left orientation 302 and the second lower left orientation 312 overlap, their mutual alignment is not orthogonal, resulting in different refraction for the two different elliptical polarizations. occurs, and thus the lens forms a double image in the region where the first lower left orientation 302 and the second lower left orientation 312 overlap. The same goes for the first lower right orientation 303 overlapping the second lower right orientation 313, the first upper left orientation 304 overlapping the second upper orientation 314, and the first upper right orientation 305 overlapping the second upper right orientation. This also applies to areas that overlap with 315.

In other words, light can be decomposed into two independent polarization states (2-fold linear, 2-fold circular, or 2-fold elliptical), and unpolarized light involves a superposition of these two states. Liquid crystals consist of elongated molecules with different refractive index values along different axes. When using a single lens cell and ideal linear alignment directions at the top and bottom surfaces, in the on state, linearly polarized light in the longitudinal direction of the molecule is lensed, and other polarized light orthogonal to said linearly polarized light is lensed. Not affected. The resulting image through the lens is therefore a double image, both magnified and unmagnified.

However, by placing a linear polarizer parallel to the linear alignment direction, the unmagnified image can be eliminated. For a double stacked lens cell with a 90 degree angle, both polarizations are increased and the incident unpolarized light is magnified overall. However, in reality, although linear alignment within the lens cell is desirable, the lens introduces misalignment. As a result, there is a location-dependent twist that changes the linearly polarized light to a location-dependent elliptically polarized light (such as the location-dependent elliptically polarized state illustrated in FIG. 3B). As a result, it is not possible to remove the unmagnified image with the help of a linear polarizer. More specifically, elliptically polarized light originating from independent linearly polarized light (each including magnified or unmagnified images) can no longer be resolved with a linear polarizer.

Furthermore, it is also difficult to make a completely polarization independent lens with two stacked cells. Eventually, at each position, it must be possible to ensure that the polarization changes in both cells are the same but rotated 90 degrees, but this requires two equal lenses as exemplified in Figure 3B. This is not possible in cells.

FIG. 4 illustrates an image in a switched-off state of an electro-active lens 101 such as the embodiment described in view of FIG. In the switched-off state, the uniaxial liquid crystal molecules are preferably aligned in the axial direction of the electro-active lens 101, ie in a direction substantially perpendicular to the surface of the first electrode 106. As such, in this state, the refractive index of the liquid crystal matches the refractive index of the Fresnel lens structure 102. As such, there is no lens action in the switched-off state. An image of a light screen (as viewed through electro-active lens 101) containing a plurality of black dots arranged in a repeating pattern is illustrated at 401. Here, the dots on the screen are also visible as a repeating pattern. Pattern 401 is the same pattern of dots placed on the screen.

When the electro-active lens 101 is switched on, the liquid crystals are preferably aligned in a radial direction, ie in a direction substantially parallel to the surface of the first electrode 106. As such, the refractive index of the liquid crystal does not match the refractive index of the Fresnel lens structure 102 and a lens effect is obtained. A light screen image containing multiple dots is magnified as illustrated in image 401. However, the magnification is not the same for two orthogonal polarizations. For example, dots 402 and 403 are separate dots belonging to different polarizations, ideally these dots coincide to form one dot, i.e. ideally a polarization independent magnification is obtained .

This problem mainly occurs in conditions where an electric field is applied on the liquid crystal layer by the electrodes, so the following description will relate to such conditions, except where clearly different.

FIG. 5 illustrates one embodiment of an electro-active lens 501 in which the problems identified above are resolved. Electro-active lens 501 includes substantially the same components as electro-active lens 101 of FIG. 1, and like reference numbers (above 400) refer to like elements. In order not to obscure the disclosure, the same description that also applies to this figure will not be repeated here. The electro-active lens 501 comprises (from top to bottom in the figure) a first substrate 504, a first electrode layer 506, an alignment layer 506, a layer of LC material 513 and a cavity 508 filled with a diffractive structure 502, a further alignment layer. 512, a second electrode layer, and a second substrate 505. Additionally, electro-active lens 501 includes a polarizer layer 560 disposed between first substrate 504 and electrode layer 506.

FIG. 6 also illustrates a further embodiment of an electro-active lens 801 in which the problems identified above are resolved. Electro-active lens 801 includes substantially the same components as electro-active lens 501 of FIG. 5, and like reference numbers (above 300) refer to like elements. In order not to obscure the disclosure, the same description that also applies to this figure will not be repeated here. In addition, the electro-active lens 801 comprises a polarizer layer 860, the function of which will be explained later. Polarizer layer 860 in this embodiment is disposed over first substrate 604 (ie, on the outer surface of first substrate 804).

FIG. 7 shows an exploded view of a lens unit 650 consisting of the optical device of FIG. 5 placed between two lens parts 651 and 652. These two lens units 650 may be placed within a frame of eyeglasses to be worn by a person, allowing the person to change the optical power of the lens units between an off state and an on state. .

In the embodiments of FIGS. 5-7, linear polarizers forming polarizer layers 560, 860 are provided. The polarizing layer is configured to pass a first linearly polarized light and substantially block a second linearly polarized light orthogonal to the first linearly polarized light. Further, the polarizer layer is aligned such that the first linearly polarized light is substantially parallel to the alignment of the liquid crystals of the liquid crystal layer 508, 808 at a location proximate the first electrode 506, 806. For example, a linear polarizer 560, 860 may pass a first transverse direction (e.g., Polarized light in the y direction perpendicular to the z direction, that is, the direction perpendicular to the xz plane) can be blocked. In this example, the alignment of the liquid crystal near the first electrode 506, 806 is in the x direction. Additionally, alignment facing the cavity 508, 808 from the outer surface of any blazes 510 of the diffractive structure 502, 802 (or the outer surface of any blaze of the second alignment layer provided above the diffractive structure 502, 802) The thickness d0 of the liquid crystal layer 508, 808 measured to the outer surface of the layer 561, 861 is such that the liquid crystal layer satisfies the Morgan condition (Equation 1). This prevents double images 401 as illustrated in FIG. 4.

Those skilled in the art will recognize that the thickness d0 may also be selected such that the Morgan condition (Equation 1) is not completely satisfied, but some waveguiding effect still occurs. For example, regarding the thickness d0,
, f≧1, and the well-known Gooch-Tully alternative condition for a 90° twist can be used to evaluate the influence of polarization state. The transmittance of such a twisted cell placed between parallel polarizers is calculated as a function of the thickness d (see Figure X). For transmittance, the minimum value is the formula
, where M is an integer [Reference: Non-Patent Document 2].

In many devices, the first minimum value of transmittance is used to define the required minimum thickness, but here the main drawback is that the first minimum value is Only the following shall be retained. Physically, this means that for the first minimum thickness, the resulting polarization state is not purely linear for most other wavelengths. In general, the polarization state will be elliptical, with the main contribution still along the preferred direction (ie, the alignment direction on the counter substrate). By increasing the integer M and performing calculations for multiple wavelengths, we obtain an optimal thickness d0 with approximately similar transmittance values, and the waveguiding conditions are considered to be fully satisfied. obtain. Therefore, substituting the thickness value on the left side of the Morgan condition, f is approximately 1, 2, 5, or 10.

The above solution still substantially solves the problem since the thickness of most regions of the liquid crystal layer 508 is substantially greater than d0 when measured from the part of the blaze 510 closest to the first electrode 506. obtain.

Additionally, the polarizing layer 560 may be arranged between the first substrate 504 and the first electrode 506 (as shown in FIG. 5), between the first electrode 806 and the first alignment layer 811, or between the first 1 substrate 804 (FIG. 6).

In principle, it is also possible to provide a polarizer layer on the side of the second substrate 505, 805, for example between the second substrate and the diffractive structure. In this case, a location-dependent quasi-spherical polarizer layer should be added. Such a location-dependent quasi-spherical polarizer is specifically a Fresnel polarizer after passing through the first substrate 504, 804, the first electrode 506, 806, the alignment layer 511, 811, and the liquid crystal layer 508, 808. Lens structures 502, 802 may be configured to filter out polarized light emerging from them. A location-dependent quasi-spherical polarizer would have a spherical shape that accurately eliminates the non-refracted polarized component of the emerging light. For this purpose, the electro-active lens 501 will have a specified pattern. For example, referring to FIG. 3, a location-dependent quasi-spherical polarizer, when incorporated into an electro-active lens having profile 300, would be positioned at each of arrows 301, 302, 303, 304, and 305, respectively. will block light having a polarization direction perpendicular to each of the arrows 301, 302, 303, 304, and 305 at a location. In this case, for each thickness d0, each Fresnel lens structure 502, and each liquid crystal layer, measurements regarding the polarization direction of the light are performed to define the Fresnel lens structure 502 at its respective position (in the xy plane) within the electro-active lens. Following such measurements, it becomes necessary to form a location-dependent quasi-spherical polarizer.

Furthermore, in the embodiments described above where there is a polarizer layer on the side of the second substrate, a second solution, from the end of any blaze 510 to the opposite end of the liquid crystal layer 508 (i.e. The thickness d0 of the liquid crystal layer measured up to (near the first electrode 506) is such that the liquid crystal layer satisfies the Morgan condition (Equation 1). This prevents double images as illustrated in FIG. 4.

Those skilled in the art will also understand that the thickness d0 may also be selected such that the Morgan condition (Equation 1) is not fully satisfied, e.g. it may be partially satisfied for the thickness d0, i.e.
, with f≧1, recognizing that, for example, f can be about 1, 2, 5, 10, or preferably from 5 to 10, or >10. The above solution still substantially solves the problem since the thickness of most regions of the liquid crystal layer 508 is substantially greater than d0 when measured from the part of the blaze 510 closest to the first electrode 506. obtain.

A person skilled in the art will recognize that the first and second solutions can be combined. This may adequately solve the problem described above. However, in some embodiments, it may not be desirable to have two polarizing layers to reduce the transmitted light intensity.

FIG. 8 illustrates a third solution to the above problem. In the illustrated embodiment, electro-active lenses 601 and 601' include substantially the same components as electro-active lens 101 of FIG. 1 (i.e., a lens without one or more polarizer layers), and similar references Numbers refer to similar elements (above number 500). In order not to obscure the disclosure, the same description that also applies to this figure will not be repeated here in its entirety.

FIG. 8 shows an optical device 600 that includes a first electro-active lens 601 and a second electro-active lens 601' stacked on top of the first electro-active lens 601. Similar to electro-active lens 101 of FIG. 'Equipped with '. The first and second optically transparent substrates 604, 604', 605, 605' extend generally parallel to each other and are axially (z) and transversely (x, y) as shown. ). The first and second electro-active lenses 601, 601' are arranged such that the second substrate 605, 605' of each of the electro-active lenses 601, 601' is on the outside of the stack and the first substrate 604, 604' of each of the electro-active lenses 601, 601' are stacked in such a way that they are placed inside the stack.

The first electro-active lens 601 and the further electro-active lens 601' are in optical communication, i.e. the second substrate 604 and the further second substrate 604' are preferably in optical communication between the two substrates. Optically coupled so that no interface exists. Similar to the electro-active lenses described in view of FIG. ) to the electrode opposite the diffractive lens structure, i.e. the electrode 606 of the first electro-active lens 601 or the electrode 606' of the second electro-active lens 601, respectively, to the respective alignment layers 611, 611'. It also has thicknesses d1 and d2. Each of the thicknesses d1 and d2 is such that the liquid crystal layer 613 of the first electro-active lens 601 and the liquid crystal layer 613' of the second electro-active lens 601' satisfy the Morgan condition (Equation 1). This prevents, or at least reduces to a significant extent, double images 401 as illustrated in FIG. 4.

The first electrode 606 and the further first electrode 606' each include an alignment layer 611, 611', for example a polyimide layer treated by rubbing. The alignments of liquid crystals on opposing surfaces of alignment layers 611 and 611' are mutually orthogonal. For example, the liquid crystals of the first liquid crystal layer 613 are aligned in the x direction on the surface close to the alignment layer 611 of the first electrode 606, and the liquid crystals of the second liquid crystal layer 613' are aligned in the y-direction (not shown, perpendicular to the x- and z-directions) on the surface near the alignment layer 611'. Thereby, the first polarization of the light incident on the first electro-active lens 601 is magnified by the first electro-active lens 601, and the second polarization ( (perpendicular to the first polarization direction) is not expanded, the expanded first polarization of the light incident on the further electro-active lens 601' cannot be further expanded by the further electro-active lens 601'. Instead, the second polarization of the light incident on the further electro-active lens 601' is magnified. Thereby, the first electro-active lens 601 and the further electro-active lens 601' making up the optical device 600 cooperate to provide polarization-independent magnification.

For manufacturing purposes, it may be preferred if d1 and d2 are the same, or that the first electro-active lens 601 and the further electro-active lens 601' are substantially the same. Thereby, both elements can be formed using the same parameters for the production method. However, in some embodiments, d1 and d2 may be different (ie, the blaze heights may be different if the diffractive lens element is a Fresnel lens element). It is even possible that the blaze position of the Fresnel lens elements of the first electro-active lens is different from the blaze position of the Fresnel lens elements of the second electro-active lens. For example, the blaze height may be slightly different on both electro-active lenses when the blaze edges do not need to be precisely aligned. In a preferred embodiment, however, the optical power of the first electro-active lens 601 is the same as the optical power of the second electro-active lens 601'.

This third solution may offer an advantage over the first and second solutions in that the intensity of the light incident on the electro-active lenses 601 and 601' is substantially conserved, but The first and second solutions reduce the intensity of the light due to at least one polarizer. On the other hand, the units according to the first and second solutions can be relatively thin compared to the third solution. Depending on the application, any one of the first, second, third, or any combination thereof may be applied.

Depending on the dimensions and desired optical qualities of the electro-active lens, an alignment layer (e.g., alignment layer 512) overlying the diffractive lens structure may also include a pretilt, with the alignment layer It has a preferred direction that is parallel to the linear alignment direction of the overlying alignment layer. Introducing this pretilt generally reduces the value of the twist angle and increases the Morgan condition value. This results in better optical performance.

FIG. 9 is a schematic exploded view of the electroactive unit of FIG. 8. Some components have been omitted here for clarity. The first electro-active lens 701 and the further electro-active lens 711 are actually in optical communication.

A liquid crystal layer and a Fresnel lens structure are disposed between the second electrode 707 and the first electrode 706 (not shown). The distance between the second electrode 707 and the first electrode 706 is such that the liquid crystal disposed therebetween satisfies the Morgan condition (Equation 1). First electrode 706 is provided with an alignment layer illustrated schematically at 730 . This is because the liquid crystals are aligned parallel to the alignment direction 730 on the first electrode 706. On the second electrode 707, the liquid crystals may be aligned according to a general pattern 731 due to the geometry of the first Fresnel lens structure (not shown). This general pattern may be a star starting from the center. The alignment pattern on the second electrode 707 is, for example, a surface in contact with the liquid crystal close to the second electrode 707 (e.g., a Fresnel lens structure or a layer provided on the surface of the electrode 707 (not including a liquid crystal layer)). Note that the rubbing of )) can also be different. For example, due to rubbing the surface near the electrode 707, the arrangement on said electrode may be similar to the orientation described in consideration of FIG. 3A.

A liquid crystal layer and a Fresnel lens structure are arranged between the further second electrode 717 and the further first electrode 716 (not shown). The distance between the further second electrode 717 and the further first electrode 716 is such that the liquid crystal disposed therebetween satisfies the Morgan condition (Equation 1). A further first electrode 716 is provided with an alignment layer illustrated schematically at 740 . Since we want to obtain a uniform linear polarization state on the further first electrode 716, the liquid crystal in the further electro-active lens 711 is aligned parallel to the alignment direction 740 on the further first electrode 716. On the further second electrode 717, the liquid crystals may be aligned according to a general pattern 741 due to the geometry of the second Fresnel lens structure (not shown). The alignment pattern on the further second electrode 717 may be, for example, a surface in contact with the liquid crystal close to the further second electrode 717 (e.g. a Fresnel lens structure or a layer provided on or on the surface of the electrode 717 (a liquid crystal layer)). Note that it may be different depending on the rubbing of (not including)). For example, due to rubbing the surface near the electrode 717, the arrangement on said electrode may be similar to the arrangement described in view of FIG. 3A.

The alignment of the first alignment direction 730 with respect to the further first alignment direction 740 is orthogonal. Thereby, if the first polarized light is expanded by the first electro-active lens 701 and the second polarization direction (orthogonal to the first polarization direction) is not expanded, the second is magnified by the further electro-active lens 711, and the first polarization direction (orthogonal to the first polarization direction) is not magnified. Thereby, both orthogonal polarization directions are expanded and polarization-independent expansion is achieved.

Exemplary Embodiments In the following non-limiting examples, an exemplary lens diameter is 21 mm, i.e., the Fresnel lens structures (such as 102, 502, 602, and 612) have diameters in the x and y directions. and both have a diameter of 21 mm.

In addition to the birefringence of the liquid crystal and the maximum twist within the cell, the cell thickness is also an important parameter. It is important to design the spacer height above the Fresnel lens structure sufficiently high to ensure that the Morgan regime is achieved throughout the lens and that the thickness varies within the Fresnel blazes. In this way, this regime is preferably achieved even above the highest point of the blaze.

Using this regime, it is possible to completely specify the linear alignment direction on the lens surface, and even use only the circularly symmetrical alignment that results from applying a homeotropic alignment layer that does not rub or undergoes a photoalignment process. It is possible. Nevertheless, in some embodiments this may be the case. Ultimately, there is a trade-off between the height of the spacer above the lens, the degree to which the Morgan regime is achieved, and the switching voltage and speed of the lens. A lens cell with a certain spacer height and a (quasi-)linear alignment direction on the lens surface (as in Figure 3A) has better optical quality compared to the same lens cell with a circularly symmetrical alignment direction on the lens surface. , because the former is deeper in the Morgan regime. A lens cell with a smaller spacer height compared to a lens cell with a (quasi-)linear alignment direction and a circularly symmetrical alignment direction may have similar optical quality, but a faster switching between off and on states. It is.

The Hartmann test was used to test electro-active lenses. The quality of the electro-active lens was determined by using the contrast value of the matrix of projected dots (such as that in Figure 4). In the following example, the electro-active lens is divided from inside to outside into three concentric zones C1, C2, and C3. The average contrast value across the zone summarizes the quality within the entire zone.

(Example 1 (not according to the present disclosure))
Hartmann test image of an electro-active lens in the off state with almost no Morgan regime. This electro-active lens has a blaze height of 16 microns, an additional spacer height of 3 microns, and a liquid crystal of Δn=0.2. This electro-active lens was rubbed on both sides of the liquid crystal layer. Presumably, the LCs are linearly aligned on the top substrate and the alignment direction is on the bottom substrate (near the Fresnel lens structure), with the alignment approximating the alignment as in FIG. 3A. The result of the off state is illustrated in item 400 of FIG. In the on state, the image is similar to item 401, where the unmagnified and magnified images overlap each other.

(Example 2 (not according to the present disclosure))
Electroactive lens in the off-state with almost no Morgan regime (Fig. 10A). The electro-active lens of this example is substantially the same as the electro-active lens of Example 1. FIG. 10A is a diagram illustrating the on state supplemented with contrast values of the individual contrast values of the Hartmann test dots. This result is obtained using a linear polarizer on the side of the upper substrate parallel to the linear alignment direction of the upper substrate. As can be seen from the values of C1, C2, and C3, the contrast value is only moderate.

As can be derived from FIG. 10A, the value of C1 is 0.553, corresponding to area AA1, and the value of C2 is 0.434, corresponding to area AA2, and the value of C3 is 0.377. , corresponds to area AA3.

(Example 3 (according to the first solution method of the present disclosure))
Electroactive lens in the on-state in the Morgan regime (FIG. 10B). This example concerns an electro-active lens in the Morgan regime where the surface of the Fresnel lens structure has been rubbed. The blaze height is 15 microns, with an additional spacer height of 10 microns, and Δn = 0.25. The electro-active lens is measured using a linear polarizer on the side of the upper substrate parallel to the linear alignment direction of the counter electrode substrate. This electro-active lens has the best contrast values (of Examples 2-4) because the maximum twist of the electro-active lens is limited.

As can be seen from FIG. 10B, the value of C1 is 0.532, which corresponds to area BA1, and the value of C2 is 0.48, which corresponds to area BA2, and the value of C3 is 0.453. , corresponds to area BA3.

(Example 4 (according to the first solution method of the present disclosure))
Electroactive lens in the on-state in the Morgan regime (Fig. 10C). This example concerns an electro-active lens in the Morgan regime where the surface of the Fresnel lens structure was not rubbed. The blaze height is 15 microns, with an additional spacer height of 10 microns, and Δn = 0.25. The electro-active lens is measured using a linear polarizer on the side of the upper substrate parallel to the linear alignment direction of the counter electrodes. The electro-active lens shows better contrast values compared to the second example exclusively in the outer C3 zone.

As can be seen in FIG. 10C, the value of C1 is 0.562, which corresponds to area CA1, and the value of C2 is 0.487, which corresponds to area CA2, and the value of C3 is 0.442. , corresponds to area CA3.

From the above examples, it can be objectively and quantitatively demonstrated that the present disclosure improves the quality of electro-active lenses.

It is to be understood that this disclosure is not limited to the particular aspects described, as such may vary. Additionally, the terminology used herein is for the purpose of describing particular aspects only and is intended to be limiting, as the scope of the disclosure is limited only by the appended claims. It should be understood that this is not the case.

101 Electro-active lens 102 Diffractive lens structure 103 Boundary 104 First substrate 105 Second substrate 106 First electrode 107 Second electrode 108 Cavity 108a, 108b Intermediate space 109 Spacer 110 Blaze 111 Alignment layer 112 Second alignment layer 113 Nematic liquid crystal (LC) layer 201 Surface 200, 210 Surface 205 Liquid crystal 300 Lens outer shape 301, 302, 303, 304, 305 Arrow 306 Direction 310 Lens outer shape 311 Second center orientation 312 Second lower left orientation 313 Second right Down orientation 314 Second up orientation 315 Second upper right orientation 400 Item 401 Enlarged image 402 Dot 403 Dot 501 Electro-active lens 502 Diffractive structure 502, 802 Diffractive structure 504 First substrate 505 Second substrate 506 First electrode Layers 506 alignment layer 506, 806 first electrode 508 cavity 508, 808 liquid crystal layer 510 blaze 511 alignment layer 512 alignment layer 513 layer of LC material 560 polarizer layer 561, 861 alignment layer 600 optical device 601, 601' electro-active lens 602, 602' diffractive structure 604 first substrate 604, 604' first optically transparent substrate 605, 605' second optically transparent substrate 606' electrode 611, 611' alignment layer 612, 612' alignment layer 613, 613' Liquid crystal layer 701 First electroactive lens 706 First electrode 707 Second electrode 711 Electroactive lens 716 First electrode 717 Second electrode 730 Alignment direction 731 General pattern 740 Alignment direction 741 General pattern 801 Electroactive Lens 804 First substrate 806 First electrode 811 First alignment layer 860 Polarizer layer

Claims (29)

An optical device for use in eyewear, the optical device comprising a first electro-active lens for adjustable transmission of light, the electro-active lens comprising - first and second optical lenses. a transparent substrate, wherein the first and second optically transparent substrates extend generally parallel to each other and define an axial (z) and a transverse direction (x,y); a transparent substrate,
- a diffractive lens structure, such as a Fresnel lens structure, arranged between the first optically transparent substrate and the second optically transparent substrate on the side of the second optically transparent substrate;
- a first optically transparent electrode formed on the first optically transparent substrate and a second optically transparent electrode formed on the second optically transparent substrate or on the diffractive lens structure; ,
- a sealed cavity (108) between the first optically transparent substrate and the second optically transparent substrate, in which the diffractive lens structure and the nematic liquid crystal are arranged; at least one LC layer of a (LC) material is disposed, the liquid crystals in the nematic liquid crystal (LC) material being generally axially aligned in an off state;
The first optically transparent electrode has a contact surface in contact with the LC layer and linearly directs the liquid crystal in the nematic liquid crystal material in the on state in a first horizontal direction by introducing a pretilt in the off state. a sealed cavity (108) comprising an alignment layer configured to align the
a polarizing element configured to condition light having a polarization in a second horizontal direction that is perpendicular to the first horizontal direction;
Equipped with
The LC layer of nematic liquid crystal material is measured between the part of the diffractive lens structure closest to the first optically transparent electrode and the contact surface of the alignment layer on the first optically transparent electrode. has a thickness (D) of
The thickness (D) is selected to satisfy the condition 1<(πD(n _e −n _o )/(φλ)<200, where n _o is the ordinary refractive index of the LC layer, and n _e is , is the extraordinary refractive index of the LC layer, φ is the twist angle of the liquid crystal director of the LC layer, λ is the wavelength of the light, and the wavelength λ is in the range of 350 nm to 750 nm. device. The diffractive lens structure, which is arranged between the first optically transparent substrate and the second optically transparent substrate on the side of the second optically transparent substrate, is arranged between the second optically transparent electrode and the second optically transparent electrode. The optical lens according to claim 1, wherein the optical lens is arranged in a. The polarizing element includes a second electro-active lens stacked on the first electro-active lens, and the second optically transparent layer of the first electro-active lens is in contact with the LC layer. an alignment layer having a contact surface and configured to linearly align liquid crystals in the nematic liquid crystal material in a first horizontal direction; The transparent layer includes an alignment layer having a contact surface in contact with the LC layer and configured to linearly align the liquid crystals in the nematic liquid crystal material in a second horizontal direction; The optical lens according to claim 1 or 2, wherein the horizontal direction is perpendicular to the second horizontal direction. The first and second electro-active lenses are stacked with respective first optically transparent substrates facing each other, and/or the first and second electro-active lenses are stacked with the respective first optically transparent substrates facing each other, and/or the first and second electro-active lenses are 4. The optical device of claim 3, stacked on top of each other such that a transparent substrate is placed on the outside of the stack and the first optically transparent substrate is placed on the inside of the stack. 4. The first optically transparent substrate of the first electro-active lens and the first optically transparent substrate of the second electro-active lens are combined into a single common optically transparent substrate. Item 4. The optical device according to item 3 or 4. 5. An optical device according to claim 3 or 4, wherein the refractive power of the first electro-active lens corresponds to the refractive power of the second electro-active lens. The diffractive lens structure is a Fresnel lens structure, and the blaze axial height and/or blaze transverse position of the Fresnel lens structure of the first electro-active lens is greater than the Fresnel lens structure of the second electro-active lens. 7. Optical device according to any one of claims 3 to 6, at least partially different from the blaze axial height and/or blaze transverse position of the structure. 8. An optical device according to any one of claims 3 to 7, wherein the diffractive lens structure of the first electro-active lens faces the diffractive lens structure of the second electro-active lens. 9. An optical device according to any one of claims 3 to 8, wherein the first and second electro-active lenses are identical. 10. An optical device according to any one of claims 3 to 9, wherein the nematic liquid crystal material of the first electro-active lens is different from the nematic liquid crystal material of the second electro-active lens. a linear polarizer configured to allow light having a first linear polarization to pass therethrough and substantially blocking light having a second linear polarization perpendicular to the first linear polarization; 5. The linear polarizer is aligned such that the first linearly polarized light is substantially parallel to the alignment of the liquid crystal in the liquid crystal layer at a location proximate the first optically transparent electrode. 3. The optical device according to 1 or 2. The first linearly polarized light is parallel to a first transverse direction (x) and the second linearly polarized light is parallel to a second transverse direction (y) perpendicular to the first transverse direction. 12. The optical device of claim 11. The linear polarizer comprises one or more polarizing layers attached to the first optically transparent substrate and/or the first optically transparent electrode, preferably attached to the alignment layer. The optical device according to claim 11 or 12, comprising a polarizing layer aligned in the alignment direction of the alignment layer. at least one polarizing layer formed on the surface of the diffractive lens structure facing the LC layer, the polarization director of the at least one further polarizing layer being aligned with the local liquid crystal director of the lens surface. 14. An optical device according to any one of claims 11 to 13, wherein the diffractive lens structure is tuned within different regions of the diffractive lens structure. The diffractive element or the second optically transparent electrode is configured to linearly align liquid crystals within the nematic liquid crystal material in the first horizontal direction in the on state by introducing a pretilt in the off state. 15. An optical device according to any one of claims 1 to 14, comprising a further alignment layer. 5. The at least one electro-active lens is configured to adjust the focusing or dispersion of light by changing the alignment of liquid crystals in the LC layer upon application of a voltage to the optically transparent electrode. 16. The optical device according to any one of Items 1 to 15. The at least one electro-active lens is configured to change the refractive power of the electro-active lens by changing the refractive index of the LC layer in the transverse direction upon application of a voltage to the optically transparent electrode. , an optical device according to any one of claims 1 to 16. Upon application of a voltage to the optically transparent electrode of the at least one electro-active lens, the at least one electro-active lens exhibits lens action from an off state in which the at least one electro-active lens exhibits substantially no lens action. 18. An optical device according to claim 16 or 17, configured to cause the at least one electro-active lens to switch to the on-state shown. In the off state, the liquid crystal in the nematic liquid crystal material is oriented such that the refractive index of the LC layer in the transverse direction substantially matches the refractive index of the diffractive lens structure, and/or in the on state 19. An optical device according to any one of claims 1 to 18, in which the orientation of the liquid crystal is tilted such that the orientation is parallel to the alignment direction of the alignment layer. 20. Optical device according to any one of claims 1 to 19, wherein the diffractive element on the second optically transparent electrode is provided with an alignment layer facing the LC layer. 21. Any one of claims 1 to 20, wherein the optically transparent electrodes of the electro-active lens are electrically connected to simultaneously switch the first electro-active lens and the second electro-active lens. Optical device described in. A plurality of spacers are arranged in the liquid crystal layer and extend in a direction perpendicular to the plane in which the second optically transparent electrode extends, the spacers preferably being formed on the diffractive lens structure. 22. An optical device according to any one of claims 1 to 21. The spacer provides an additional height of between 1 and 20 μm, preferably between 2 and 12 μm, when measured from the part of the diffractive lens structure closest to the second optically transparent substrate. 23. The optical device of claim 22, configured to. Optical device according to any one of claims 1 to 23, wherein the nematic liquid crystal material of the at least one electro-active lens has a birefringence Δn lying in the range 0.15 to 0.40. 25. An optical device according to any preceding claim, wherein the optical device is configured to provide polarization-independent transmission of light. A lens unit for use in eyeglasses, the lens unit comprising a first lens component, a second lens component, and an optical device according to any one of claims 1 to 25. , wherein the electro-active lens is arranged, preferably sandwiched, between the first lens part and the second lens part. Eyeglasses comprising a frame on which the first and second lens units according to claim 26 or the first and second optical devices according to any one of claims 1 to 25 are mounted. Use of an optical device according to any one of claims 1 to 25. An alternating current voltage is applied to the first and second optically transparent electrodes of the first electro-active lens and the second electro-active lens stacked on the first electro-active lens to 11. A method of operating an optical device according to any one of claims 3 to 10, comprising aligning the liquid crystal in a direction substantially perpendicular to the first and second optically transparent substrates.

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